Air spring with damping characteristics for heavy-duty vehicles

ABSTRACT

An air spring with damping characteristics for a suspension assembly of a heavy-duty vehicle includes a bellows and a piston. The bellows includes a bellows chamber. The bellows is attached to a main member of the heavy-duty vehicle and to the piston. The piston includes an open bottom that is sealingly closed by a disc attached to the open bottom. The piston and the disc define a piston chamber. The piston is mounted on the suspension assembly of the heavy-duty vehicle. The bellows chamber and the piston chamber are in fluid communication with each other via at least one opening, wherein airflow between the bellows chamber and the piston chamber provides damping to the suspension assembly of the heavy-duty vehicle.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. application Ser.No. 15/150,505 filed on May 10, 2016, which claims the benefit of U.S.Provisional Patent Application Ser. No. 62/159,528, filed May 11, 2015.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates generally to the art of axle/suspension systemsfor heavy-duty vehicles. More particularly, the invention relates toair-ride axle/suspension systems for heavy-duty vehicles, which utilizean air spring to cushion the ride of the vehicle. More specifically, theinvention is directed to the conversion of a non-damping air spring toan air spring with damping characteristics, which is accomplished bysealing the non-damping air spring piston to create a piston chamber andproviding fluid communication between the piston chamber and a bellowschamber of the air spring in order to provide damping characteristics tothe air spring.

Background Art

The use of one or more air-ride trailing and leading arm rigid beam-typeaxle/suspension systems has been popular in the heavy-duty truck andtractor-trailer industry for many years. Although such axle/suspensionsystems can be found in widely varying structural forms, in generaltheir structure is similar in that each system typically includes a pairof suspension assemblies. In some heavy-duty vehicles, the suspensionassemblies are connected directly to the primary frame of the vehicle.In other heavy-duty vehicles, the primary frame of the vehicle supportsa subframe, and the suspension assemblies connect directly to thesubframe. For those heavy-duty vehicles that support a subframe, thesubframe can be non-movable or movable, the latter being commonlyreferred to as a slider box, slider subframe, slider undercarriage, orsecondary slider frame. For the purpose of convenience and clarity,reference herein will be made to main members, with the understandingthat such reference is by way of example, and that the present inventionapplies to heavy-duty vehicle axle/suspension systems suspended frommain members of: primary frames, movable subframes and non-movablesubframes.

Specifically, each suspension assembly of an axle/suspension systemincludes a longitudinally extending elongated beam. Each beam typicallyis located adjacent to and below a respective one of a pair ofspaced-apart longitudinally extending main members and one or more crossmembers, which form the frame of the vehicle. More specifically, eachbeam is pivotally connected at one of its ends to a hanger, which inturn is attached to and depends from a respective one of the mainmembers of the vehicle. An axle extends transversely between andtypically is connected by some means to the beams of the pair ofsuspension assemblies at a selected location from about the mid-point ofeach beam to the end of the beam opposite from its pivotal connectionend. The opposite end of each beam also is connected to an air spring,or its equivalent, either directly or via a pedestal, and the air springis in turn connected to a respective one of the main members. The airspring cushions the ride of the axle/suspension system during operationand, in some cases, provides damping characteristics. In those caseswhere the air spring does not provide damping, one or more shockabsorbers are employed to provide damping. A height control valve ismounted on the hanger or other support structure and is operativelyconnected to the beam and to the air spring in order to maintain theride height of the vehicle. A brake system is also included on thevehicle axle/suspension system. The beam may extend rearwardly orfrontwardly from the pivotal connection relative to the front of thevehicle, thus defining what are typically referred to as trailing arm orleading arm axle/suspension systems, respectively. However, for purposesof the description contained herein, it is understood that the term“trailing arm” will encompass beams which extend either rearwardly orfrontwardly with respect to the front end of the vehicle.

The axle/suspension systems of the heavy-duty vehicle act to cushion theride, dampen vibrations and stabilize the vehicle. More particularly, asthe vehicle is traveling over the road, its wheels encounter roadconditions that impart various forces, loads, and/or stresses,collectively referred to herein as forces, to the respective axle onwhich the wheels are mounted, and in turn, to the suspension assembliesthat are connected to and support the axle. In order to minimize thedetrimental effect of these forces on the vehicle and/or its cargo as itis operating, the axle/suspension system is designed to react and/orabsorb at least some of them.

These forces include vertical forces caused by vertical movement of thewheels as they encounter certain road conditions, fore-aft forces causedby acceleration and deceleration of the vehicle due to operation of thevehicle and/or road conditions, and side-load and torsional forcesassociated with transverse vehicle movement, such as turning of thevehicle and lane-change maneuvers. In order to address such disparateforces, axle/suspension systems have differing structural requirements.More particularly, it is desirable for an axle/suspension system tominimize the amount of sway experienced by the vehicle and thus providewhat is known in the art as roll stability. However, it is alsodesirable for an axle/suspension system to be relatively flexible toassist in cushioning the vehicle from vertical impacts, and to providecompliance so that the components of the axle/suspension system resistfailure, thereby increasing durability of the axle/suspension system. Itis also desirable to dampen the vibrations or oscillations that resultfrom such forces in order to reduce wheel and/or suspension bounce,which in turn can potentially harm the wheels and the components of theaxle/suspension system, thereby reducing optimal ride characteristics ofthe axle/suspension system and the life of the components of theaxle/suspension system. A key component of the axle/suspension systemthat cushions the ride of the vehicle from vertical impacts is the airspring or other spring mechanism, such as a coil spring or a leafspring, while a shock absorber typically provides damping to theaxle/suspension system. In some instances, the air spring can alsoprovide damping to the axle/suspension system.

The typical air spring of the type utilized in heavy-duty air-rideaxle/suspension systems includes three main components: a flexiblebellows, a bellows top plate, and a piston. The bellows is typicallyformed from rubber or other flexible material, and is sealingly engagedwith the bellows top plate and also to the top portion of the piston.The volume of pressurized air, or “air volume”, that is contained withinthe air spring is a major factor in determining the spring rate of theair spring. More specifically, this air volume is contained within thebellows and, in some cases, the piston of the air spring. Usually, thelarger the air volume of the air spring, the lower the spring rate ofthe air spring. A lower spring rate is generally more desirable in theheavy-duty vehicle industry because it allows for softer ridecharacteristics for the vehicle. Typically, the piston either contains ahollow cavity, which is in communication with the bellows and which addsto the air volume of the air spring by allowing unrestrictedcommunication of air between the piston and the bellows volumes, or thepiston has a generally hollow cylindrical-shape and does not communicatewith the bellows volume, whereby the piston does not contribute to theair volume of the air spring. In any event, the air volume of the airspring is in fluid communication with an air source, such as an airsupply tank, and also is in fluid communication with the height controlvalve of the vehicle. The height control valve, by directing air flowinto and out of the air spring of the axle/suspension system, helpsmaintain the desired ride height of the vehicle. Most prior art airsprings of the non-damping variety utilize a “molded-in” end closurethat is attached to the top plate of the piston by a fastener. In thisdesign, the bottom end of the bellows is integrally molded with a metalend closure, so that the end closure is typically not removable from thebellows. These types of air springs make up a majority of thenon-damping air spring market and typically do not exhibit thedisadvantages of the “take-apart” design described below.

Prior art air springs such as the one described above, while providingcushioning to the vehicle cargo and occupant(s) during operation of thevehicle, provide little if any damping characteristics to theaxle/suspension system. Such damping characteristics are insteadtypically provided by a pair of hydraulic shock absorbers, although asingle shock absorber has also been utilized and is generally well knownin the art. Each one of the shock absorbers is mounted on and extendsbetween the beam of a respective one of the suspension assemblies of theaxle/suspension system and the hanger mounted on a respective one of themain members of the vehicle. These shock absorbers add complexity andweight to the axle/suspension system. Moreover, because the shockabsorbers are a service item of the axle/suspension system that willrequire maintenance and/or replacement from time to time, they also addadditional maintenance and/or replacement costs to the axle/suspensionsystem.

The amount of cargo that a vehicle may carry is governed by local,state, and/or national road and bridge laws. The basic principle behindmost road and bridge laws is to limit the maximum load that a vehiclemay carry, as well as to limit the maximum load that can be supported byindividual axles. As a result, the weight of the shock absorbersundesirably reduces the amount of cargo that can be carried by theheavy-duty vehicle. Depending on the shock absorbers employed, they alsoadd varying degrees of complexity to the axle/suspension system, whichis also undesirable.

Because of the undesirable increased weight to the axle/suspensionsystem attributed to the shock absorbers, prior art air springs withdamping characteristics were developed. Prior art air springs withdamping characteristics enabled removal of the shock absorbers whilemaintaining desirable soft ride characteristics. More specifically,prior art air springs with damping characteristics typically includedopenings between the bellows and the piston in order to allow fluidcommunication between the volume of the bellows chamber and the volumeof the piston chamber. This fluid communication between the bellowschamber volume and the piston chamber volume provided dampingcharacteristics to the air spring while maintaining a soft ride to thevehicle during operation. Prior art air springs with dampingcharacteristics are typically of the “take-apart” design variety,meaning that the bottom end of the bellows of the air spring isoperatively connected to a protrusion that extends upwardly from thepiston top plate that is formed with a barb. In these types of airsprings, the bellows can be taken apart from the piston. However, airsprings having the “take-apart” design are limited during rebound traveland jounce travel and can experience fold in issues in “low pressure” or“no air” situations.

Although prior art air springs with damping characteristics provide asofter ride during vehicle operation, they typically require a customdesigned air spring piston for each specific application. Morespecifically, each anticipated use of the axle/suspension systemrequires certain damping characteristics, which, in turn, requires adifferent air spring configuration. As a result, each prior art airspring with damping characteristics requires a different custom designand manufacturing process. This leads to undesirable increases in bothdesign and manufacturing costs and an undesirable increase in productiontime for the air spring. Moreover, the “take-apart” design of the airsprings with damping characteristics potentially limits rebound traveland jounce travel and potentially exacerbates fold in issues in “lowpressure” or “no air” situations. The air spring for heavy-duty vehiclesof the present invention overcomes the problems associated with priorart non-damping air springs by removing the prior art shock absorber andconverting the non-damping air spring with a “molded-in” end closureinto an air spring that provides damping characteristics. It also allowsfor the use of different piston/pedestal combinations to be used in theair spring so that the volume of the piston can be varied along with theopening size between the piston chamber and the bellows chamber tooptimize the damping characteristics of the air spring. Additionally,the air spring for heavy-duty vehicles of the present invention providesan air spring with damping characteristics that may be optimized fordifferent uses without requiring custom design and manufacturing of theair springs for each specific use, as is typically required by prior artair springs with damping characteristics.

SUMMARY OF THE INVENTION

Objectives of the present invention include providing an air spring withdamping characteristics for heavy-duty vehicles that enables removal ofshock absorbers while maintaining desirable soft ride and dampingcharacteristics.

Another objective of the present invention is to provide an air springwith damping characteristics for heavy-duty vehicles that in certainapplications is free of the “take-apart” design so that the air springdoes not experience fold in issues in “lower pressure” or “no air”situations.

A further objective of the present invention is to provide an air springwith damping characteristics for heavy-duty vehicles that enables one toconvert a non-damping air spring with a “molded-in” or “take-apart” endclosure into an air spring providing damping characteristics.

Yet another objective of the present invention is to provide an airspring with damping characteristics for heavy-duty vehicles that allowsfor the use of different piston/pedestal combinations to be used in theair spring, so that the volume of the piston can be varied along withthe opening size between the piston chamber and the bellows chamber tooptimize the damping characteristics of the air spring.

Still another objective of the present invention is to provide an airspring with damping characteristics for heavy-duty vehicles that may beoptimized for different uses without requiring custom design andmanufacturing of the air springs for each specific use.

These objectives and advantages are obtained by the air spring withdamping characteristics for heavy-duty vehicles of the present inventionwhich includes a bellows and a piston. The bellows includes a bellowschamber and is attached to a main member of the heavy-duty vehicle, andto the piston. The piston having an open bottom which is sealinglyclosed by a disc attached to it, whereby the piston and the disc definea piston chamber. The bellows chamber and the piston chamber are influid communication with each other via at least one opening, whereinairflow between the bellows chamber and the piston chamber providesdamping to the suspension assembly of the heavy-duty vehicle.

These objectives and advantages are also obtained by the method forconverting a non-damping air spring into an air spring with dampingcharacteristics for a suspension assembly of a heavy-duty vehicle,comprising the following steps, a) providing a bellows and a piston, thebellows including a bellows chamber, the bellows chamber attached to amain member of the heavy-duty vehicle and attached to the piston, thepiston having an open bottom, b) sealingly closing the open bottom ofthe piston by attaching a disc to the open bottom, whereby the pistonand the disc define a piston chamber, the piston mounted on thesuspension assembly of the heavy-duty vehicle, the bellows chamber andthe piston chamber being in fluid communication with each other via atleast one opening, wherein airflow between the bellows chamber and thepiston chamber provides damping to the suspension assembly of theheavy-duty vehicle.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The preferred embodiments of the present invention, illustrative of thebest mode in which applicants have contemplated applying the principles,are set forth in the following description and are shown in thedrawings, and are particularly and distinctly pointed out and set forthin the appended claims.

FIG. 1 is a top rear driver side perspective view of an axle/suspensionsystem incorporating a pair of prior art non-damping air springs,showing each air spring mounted directly to a respective one of theaxle/suspension system beams, and further showing a pair of shockabsorbers, with each one of the pair of shock absorbers mounted on arespective one of the suspension assemblies of the axle/suspensionsystem;

FIG. 2 is a fragmentary rear perspective view of the axle/suspensionsystem shown in FIG. 1 incorporating an alternative prior artnon-damping air spring that utilizes a beam mounting pedestal, andshowing a piston of the air spring attached to the beam utilizing thebeam mounting pedestal;

FIG. 3 is a fragmentary elevation view, in section, of theaxle/suspension system and the prior art non-damping air spring shown inFIG. 2, and showing the piston of the air spring attached to the beamutilizing the beam mounting pedestal;

FIG. 4 is a perspective view of a prior art air spring with dampingcharacteristics in section, showing a pair of openings in a piston topplate that facilitate fluid communication between a piston chamber and abellows chamber of the air spring;

FIG. 5 is a fragmentary rear perspective view of a prior artaxle/suspension system incorporating a first exemplary embodiment airspring of the present invention with a portion of the air spring shownin phantom lines;

FIG. 6 is a fragmentary elevation view, in section, of the firstexemplary embodiment air spring of the present invention shown in FIG.5, showing the bellows mounted on a piston of the air spring and showinga disc mounted on the underside of the piston, and also showing anopening formed between the piston chamber and the bellows chamber toprovide fluid communication between the piston chamber and the bellowschamber of the air spring;

FIG. 7 is a fragmentary bottom perspective view of the first exemplaryembodiment air spring of the present invention shown in FIG. 5, showingthe disc being installed on the bottom of the air spring piston;

FIG. 8 is a fragmentary rear perspective view of a prior artaxle/suspension system incorporating a second exemplary embodiment airspring of the present invention, showing a disc integrated with a beammounting pedestal and attached to the bottom of a piston to create apiston chamber, with the integrated disc also attaching the piston ofthe second exemplary embodiment air spring to a beam of theaxle/suspension system with a portion of the air spring shown in phantomlines;

FIG. 9 is a fragmentary elevation view, in section, of the piston shownin FIG. 8;

FIG. 10 is a fragmentary elevation view of a third exemplary embodimentair spring of the present invention, showing a bellows mounted on apiston of the air spring, and showing a disc mounted on the bottom ofthe piston to create a piston chamber, and further showing fluidcommunication between the bellows chamber and the piston chamber via ahollow threaded rod and a conduit;

FIG. 11 is a fragmentary bottom perspective view of the third exemplaryembodiment air spring shown in FIG. 10, showing the disc being installedon the bottom of the air spring;

FIG. 12 is a top perspective view of an alternative configuration of thedisc shown in FIGS. 5-10; and

FIG. 13 is a top perspective view of another configuration of the discshown in FIGS. 5-10.

Similar numerals refer to similar parts throughout the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In order to better understand the environment in which the air springwith damping characteristics for a heavy-duty vehicle of the presentinvention is utilized, a trailing arm overslung beam-type air-rideaxle/suspension system that incorporates a prior art air spring 24, isindicated generally at 10, is shown in FIGS. 1 and 2, and now will bedescribed in detail below.

It should be noted that axle/suspension system 10 is typically mountedon a pair of longitudinally-extending spaced-apart main members 12 (FIG.2, only one shown) of a heavy-duty vehicle, which is generallyrepresentative of various types of frames used for heavy-duty vehicles,including primary frames that do not support a subframe and primaryframes and/or floor structures that do support a subframe. For primaryframes and/or floor structures that do support a subframe, the subframecan be non-movable or movable, the latter being commonly referred to asa slider box. Because axle/suspension system 10 generally includes anidentical pair of suspension assemblies 14, for sake of clarity only oneof the suspension assemblies will be described below.

Suspension assembly 14 is pivotally connected to a hanger 16 via atrailing arm overslung beam 18. More specifically, beam 18 is formedhaving a generally upside-down integrally formed U-shape with a pair ofsidewalls 66 and a top plate 65, with the open portion of the beamfacing generally downwardly. A bottom plate 67 (FIG. 2) extends betweenand is attached to the lowermost ends of sidewalls 66 by any suitablemeans such as welding to complete the structure of beam 18. Trailing armoverslung beam 18 includes a front end 20 having a bushing assembly 22,which includes a bushing, pivot bolts and washers as are well known inthe art, to facilitate pivotal connection of the beam to hanger 16. Beam18 also includes a rear end 26, which is welded or otherwise rigidlyattached to a transversely-extending axle 32.

With continued reference to FIGS. 1 and 2 and with additional referenceto FIG. 3, suspension assembly 14 also includes air spring 24, mountedon and extending between beam rear end 26 and main member 12 (FIG. 2).Air spring 24 includes a bellows 41 and a piston 42. The top portion ofbellows 41 is sealingly engaged with a bellows top plate 43. An airspring mounting plate 44 (FIGS. 1 and 2) is mounted on bellows top plate43 by fasteners 45 which are also used to mount the top portion of airspring 24 to the vehicle main member 12. Piston 42 is generallycylindrical-shaped and includes a sidewall 69, a generally flat bottomplate 50, and a top plate 82. The bottom portion of bellows 41 issealingly engaged with piston top plate 82 in a manner well known in theart utilizing a “molded-in” end closure or retaining plate 86.

As shown in FIGS. 2 and 3, prior art non-damping air spring 24 includesa bumper 81 that is mounted on piston top plate 82 by a nut 84 which isthreaded onto a fastener 136. Bumper 81 serves as a cushion betweenpiston top plate 82 and the underside of bellows top plate 43 in orderto prevent the plates from damaging one another during operation of thevehicle during “low pressure” or “no air” events.

With particular reference to FIG. 3, piston 42 of prior art air spring24 is formed with a central hub 52 attached to sidewall 69 in awell-known manner. A plurality of ribs 72 extend radially between hub 52and sidewall 69 to provide structural support to prior art air spring24.

A first configuration for mounting piston bottom plate 50 directly tobeam top plate 65 at beam rear end 26 is shown generally in FIG. 1. Inthis configuration bottom plate 50 of piston 42 is attached directly tobeam rear end 26 via fasteners (not shown). A second configuration formounting prior art air spring 24 to beam 18 will be discussed below inconnection with FIGS. 2 and 3.

As shown in FIGS. 2-3, prior art air spring 24 may alternatively bemounted on beam 18 via a beam mounting pedestal 130. With particularreference to FIG. 3, more specifically, beam mounting pedestal 130includes a generally flat base 131 for contacting and seating on beamtop plate 65 at beam rear end 26. Beam mounting pedestal 130 furtherincludes an upwardly extending column 132, which is formed with anopening 133. Fastener 136 is disposed through opening 133 and a nut 134is threaded onto the fastener to attach piston 42 to beam mountingpedestal 130 as known in the art. A pair of strengthening webs 135 (FIG.2) extend outwardly from column 132 on flat base 131. A pair of openings(not shown) are formed in flat base 131. Each opening (not shown)receives a fastener (not shown) for attaching beam mounting pedestal 130to beam top plate 65 at beam rear end 26. It should be understood thatother types of beam mounting attachments having different structures arealso known in the art and are used to mount the air spring to the beam.

With continued reference to FIGS. 2-3, prior art air spring 24 includesbellows top plate 43, piston top plate 82, and bellows 41 defining abellows chamber 98. Because the bottom of piston 42 is open and thepiston does not communicate with bellows chamber 98, the piston does notgenerally contribute any appreciable volume to air spring 24.

Referring now to FIGS. 1 and 2, the top end of a shock absorber 40(FIG. 1) is mounted on an inboardly extending wing 17 of hanger 16 via amounting bracket 19 and a fastener 15, in a manner well known in theart. The bottom end of shock absorber 40 is mounted to beam 18 (themount not shown) in a manner well known to those having skill in theart. For the sake of relative completeness, a brake system 28 includinga brake chamber 30 is shown mounted on prior art suspension assembly 14.

As mentioned above, axle/suspension system 10 is designed to absorbforces that act on the vehicle as it is operating. More particularly, itis desirable for axle/suspension system 10 to be rigid or stiff in orderto resist roll forces and thus provide roll stability for the vehicle.This is typically accomplished by using beam 18, which is rigid, andalso is rigidly attached to axle 32. It is also desirable, however, foraxle/suspension system 10 to be flexible to assist in cushioning thevehicle (not shown) from vertical impacts and to provide compliance sothat the axle/suspension system resists failure. Such flexibilitytypically is achieved through the pivotal connection of beam 18 tohanger 16 with bushing assembly 22. Air spring 24 and shock absorber 40also assist in cushioning the ride for cargo and passengers.

Prior art air spring 24 has very limited or no damping capabilitiesbecause its structure, as described above, does not provide for thesame. Instead, prior art air spring 24 relies on shock absorbers 40 toprovide damping to axle/suspension system 10. Because each shockabsorber 40 is relatively heavy, this adds weight to axle/suspensionsystem 10 and therefore reduces the amount of cargo that can be carriedby the heavy-duty vehicle. Shock absorbers 40 also add complexity toaxle/suspension system 10. Moreover, because shock absorbers 40 are aservice item of axle/suspension system 10 that will require maintenanceand/or replacement from time to time, they also add additionalmaintenance and/or replacement costs to the axle/suspension system.

Turning now to FIG. 4, a prior art air spring 124 with dampingcharacteristics is shown, which is typically used without shockabsorbers. Prior art air spring 124 is typically incorporated into anaxle/suspension system such as axle/suspension system 10 (FIG. 1), orother similar air-ride axle/suspension systems. Air spring 124 includesa bellows 141, a bellows top plate 143, and a piston 142. The top end ofbellows 141 is sealingly engaged with bellows top plate 143 in a mannerwell known in the art. An air spring mounting plate (not shown) istypically mounted on the top surface of bellows top plate 143 byfasteners (not shown) which are also used to mount the top portion ofair spring 124 to a respective one of the main members (not shown) ofthe vehicle. Alternatively, bellows top plate 143 could also be mounteddirectly on a respective one of the main members (not shown) of thevehicle.

Piston 142 is generally cylindrical-shaped and includes a sidewall 144attached to a generally flat bottom plate 150. Piston 142 also includesa top plate 182. Bottom plate 150 is formed with an upwardly extendingcentral hub 152 and is attached to sidewall 144 in a well-known manner.Central hub 152 includes a bottom plate 154 formed with a centralopening 153. A fastener 151 is disposed through opening 153 and isutilized to attach piston 142 directly to the beam (not shown), similarto the mount of prior art air spring 24 shown in FIG. 1.

Piston top plate 182, sidewall 144, and bottom plates 150 and 154 ofpiston 142 define a piston chamber 199. Sidewall 144 of piston 142includes a circular upwardly extending protrusion 183 having a lip orbarb 180 around its circumference. Barb 180 cooperates with the bottomterminal end of bellows 141 to form an airtight seal between the bellowsand the barb around the circumference of protrusion 183 of piston 142,as is well known to those of ordinary skill in the art and is known as a“take-apart” design. Additionally, bellows 141, bellows top plate 143,and piston top plate 182 define a bellows chamber 198.

A bumper 181 extends into bellows chamber 198 and is rigidly attached toa bumper mounting plate 186 by means generally well known in the art.Bumper mounting plate 186 is in turn mounted on piston top plate 182 bya fastener 184. Bumper 181 is formed from rubber, plastic or othercompliant material and extends upwardly from the top surface of bumpermounting plate 186. Additionally, bumper 181 serves as a cushion betweenpiston top plate 182 and the underside of bellows top plate 143 in orderto prevent the plates from damaging one another in the event that thepiston top plate and the underside of the bellows top plate contact oneanother during operation of the vehicle. Piston top plate 182 is formedwith a pair of openings 185, which allow a volume V₁ of the pistonchamber 199 and a volume V₂ of the bellows chamber 198 to communicatewith one another. More specifically, openings 185 allow fluid or air topass between piston chamber 199 and bellows chamber 198 during operationof the vehicle. Openings 185, piston chamber 199 and bellows chamber 198require custom design and manufacture for different applications toachieve optimal damping. As a result, prior art piston 142 is expensiveto design and manufacture for each specific axle/suspension systemapplication.

Although prior art air spring 124 does provide sufficient dampingcharacteristics, the manufacturing process of the prior art spring withdamping characteristics requires a custom designed piston 142 thusundesirably increasing design and manufacturing costs. Moreover, the“take-apart” design of prior art air spring 124 with dampingcharacteristics, may potentially limit rebound travel and jounce traveland may potentially exacerbate fold in issues in “low pressure” or “noair” situations. The air spring of the present invention overcomes theproblems associated with prior art air springs 24, 124, by providing amethod for converting an existing non-damping air spring having a“molded-in” or “take-apart” end closure into an air spring with dampingfeatures, thus minimizing both design and manufacturing costs as well asproduction costs. The air spring of the present invention will now bedescribed in detail below.

Turning to FIG. 5, a first exemplary embodiment air spring 224 of thepresent invention is shown mounted on a prior art axle/suspension system10, described in detail above. First exemplary embodiment air spring 224is similar to prior art air spring 24 with respect to its structure, butwith some differences that include modification to provide dampingcharacteristics by including a circular disc 270, an opening 274 (FIG.6), and an opening 275 (FIG. 6), as will be described in detail below.

With additional reference to FIGS. 6 and 7, first exemplary embodimentair spring 224 generally includes a bellows 241, a bellows top plate243, and a piston 242. Bellows top plate 243 includes a pair offasteners 245, each formed with an opening 246. Fasteners 245 areutilized to mount air spring 224 to an air spring plate (not shown),that in turn is mounted to main member 12 (FIG. 5). Piston 242 isgenerally cylindrical-shaped and includes a sidewall 244, a flaredportion 247, and a top plate 282.

With particular reference to FIG. 6, a bumper 281 is disposed on a topsurface of a retaining plate 286 (FIG. 6). Retaining plate 286, bumper281 and piston top plate 282 are each formed with an aligned opening260, 262, and 264, respectively. A fastener 251 is disposed throughpiston top plate opening 264, retaining plate opening 260, and bumperopening 262. A washer 283 and a nut 284 are disposed on fastener 251 tomount bumper 281 and retaining plate 286 on the top surface of pistontop plate 282. Retaining plate 286 includes a flared end 280 that ismolded into the lower end of bellows 241, which holds the bellows inplace on piston 242 and forms an airtight seal between the bellows andthe piston. Thus, first exemplary embodiment air spring 224 is known asa “molded-in” air spring design. It should be understood that flared end280 of retaining plate 286 could also be separate from the lower end ofbellows 241, whereby the flared end would capture and hold the lower endof the bellows in place on piston 242 to form an airtight seal betweenthe bellows and the piston, without changing the overall concept oroperation of the of the present invention. Bellows 241, retaining plate286, and bellows top plate 243 generally define a bellows chamber 298having an interior volume V₂ at standard ride height. Bellows chamber298 preferably has a volume of from about 305 in.³ to about 3000 in.³.More preferably, bellows chamber 298 has a volume of about 485 in.³.Bumper 281 is formed from rubber, plastic or other compliant materialand extends generally upwardly from retaining plate 286 mounted onpiston top plate 282. Bumper 281 serves as a cushion between piston topplate 282 and the underside of bellows top plate 243 in order to preventthe plates from damaging one another during operation of the vehicle.

First exemplary embodiment air spring 224 is formed with an upwardlyextending central hub 252 attached to sidewall 244 in a well-knownmanner. Central hub 252 is formed with an opening 253 that is continuouswith piston top plate opening 264. A plurality of ribs 272 (FIG. 7)extend radially between central hub 252 and sidewall 244 to providestructural support to air spring 224 of the present invention.

In accordance with one of the primary features of the present invention,as more clearly shown in FIGS. 6 and 7, generally circular disc 270 isattached or mated to the bottom of piston 242 of first exemplaryembodiment air spring 224 of the present invention. Circular disc 270 isformed with an opening 276 that aligns with opening 253 of pistoncentral hub 252. Fastener 251 extends downwardly through piston centralhub opening 253, through disc opening 276, through an opening (notshown) formed in beam mounting pedestal 130, and through an opening (notshown) formed in beam rear end top plate 65. A nut (not shown) isthreaded onto the bottom end of fastener 251 to sealingly attachcircular disc 270 to first exemplary embodiment air spring 224, and alsoattaches piston 242 of air spring 224 to beam 18. Once attached, a topsurface 289 of circular disc 270 is mated to a lower surface 287 ofsidewall 244 of piston 242 of first exemplary embodiment air spring 224to provide an airtight seal between circular disc 270 and piston 242.Circular disc 270 is formed with a continuous raised lip 278 on its topsurface along the periphery of the disc, with the lip being disposedgenerally between flared portion 247 and sidewall 244 of piston 242 whencircular disc 270 is mated to the piston. Optionally, the attachment ofcircular disc 270 to piston 242 may be supplemented by additionalattachment means such as welding, soldering, crimping, friction welding,an O-ring, a gasket, adhesive or the like. Alternatively, the attachmentof circular disc 270 to piston 242 may be accomplished via means otherthan fastener 251, such as other types of fasteners, welding, soldering,crimping, friction welding, adhesives and the like, without changing theoverall concept or operation of the present invention. Circular disc 270may be composed of metal, plastic, and/or composite material, or othermaterials known to those skilled in the art, without changing theoverall concept or operation of the present invention. Circular disc 270may optionally include a groove (not shown) formed in top surface 289disposed circumferentially around the disc, and configured to mate witha downwardly extending hub of the piston in order to reinforce theconnection of the disc to the bottom of piston 242. An O-ring or gasketmaterial could optionally be disposed in the groove to ensure anairtight fit of circular disc 270 to piston 242.

With continued reference to FIGS. 5-7, once circular disc 270 isattached to piston 242, top plate 282, sidewall 244, and the disc,define a piston chamber 299 having an interior volume V₁. Piston chamber299 is generally able to withstand the required burst pressure of theaxle/suspension system 10 during vehicle operation. Piston chamber 299preferably has a volume of from about 105 in.³ to about 550 in.³. Morepreferably, piston chamber 299 has a volume of about 240 in.³.

In accordance with another of the primary features of the presentinvention, opening 274 is formed in retaining plate 286 and alignedopening 275 is formed in top plate 282 of piston 242. More particularly,aligned openings 274, 275 are disposed generally adjacent to bumper 281.Openings 274, 275 are generally cylindrical-shaped but may include othershapes including oval, elliptical or other shapes without changing theoverall concept or operation of the present invention. Aligned openings274,275 together form a continuous opening 279 that allows pistonchamber 299 to fluidly communicate with bellows chamber 298.Alternatively, openings 274, 275 may include a spring pin (not shown),or a self-tapping screw with an integral opening, or other similarconduit that provides communication of fluid or air between pistonchamber 299 and bellows chamber 298 during operation of the vehicle. Inthis manner, damping characteristics are provided to first exemplaryembodiment air spring 224 of the present invention. Opening 279preferably has a cross sectional area of from about 0.009 in.² to about0.13 in.². More preferably, opening 279 has a cross sectional area ofabout 0.06 in.².

It is contemplated that the ratio of the cross-sectional area of opening279 measured in in.² to the volume of piston chamber 299 measured inin.³ to the volume of bellows chamber 298 measured in in.³ is in therange of ratios of from about 1:403:2,346 to about 1:61,111:333,333.This is an inclusive range that could be alternatively expressed as1:403-61,111:2,346-333,333, including any combination of ratios inbetween, and, for example, would necessarily include the followingratios 1:403:333,333 and 1:61,111:2,346.

More specifically, when axle 32 of axle/suspension system 10 experiencesa jounce event, such as when the vehicle wheels encounter a curb or araised bump in the road, the axle moves vertically upwardly toward thevehicle chassis. In such a jounce event, bellows chamber 298 iscompressed by axle/suspension system 10 as the wheels of the vehicletravel over the curb or the raised bump in the road. The compression ofair spring bellows chamber 298 causes the internal pressure of thebellows chamber to increase. Therefore, a pressure differential iscreated between bellows chamber 298 and piston chamber 299. Thispressure differential causes air to flow from bellows chamber 298,through continuous opening 279 and into piston chamber 299. The flow ofair between bellows chamber 298 into piston chamber 299 through opening279 causes damping to occur. As an additional result of the airflowthrough continuous opening 279, the pressure differential betweenbellows chamber 298 and piston chamber 299 is reduced. Air continues toflow through opening 279 until the pressures of piston chamber 299 andbellows chamber 298 have equalized.

Conversely, when axle 32 of axle/suspension system 10 experiences arebound event, such as when the vehicle wheels encounter a large hole ordepression in the road, the axle moves vertically downwardly away fromthe vehicle chassis. In such a rebound event, bellows chamber 298 isexpanded by axle/suspension system 10 as the wheels of the vehicletravel into the hole or depression in the road. The expansion of airspring bellows chamber 298 causes the internal pressure of the bellowschamber to decrease. As a result, a pressure differential is createdbetween bellows chamber 298 and piston chamber 299. This pressuredifferential causes air to flow from piston chamber 299, throughcontinuous opening 279 and into bellows chamber 298. The flow of airthrough opening 279 causes damping to occur. As an additional result ofthe airflow through opening 279, the pressure differential betweenbellows chamber 298 and piston chamber 299 is reduced. Air will continueto flow through continuous opening 279 until the pressures of pistonchamber 299 and bellows chamber 298 have equalized. When little or nosuspension movement has occurred over a period of several seconds, thepressure of bellows chamber 298 and piston chamber 299 can be consideredequal.

As a result of attaching circular disc 270 to piston 242, and providingopening 274 in retaining plate 286 and opening 275 in top plate 282 ofthe piston, collectively, continuous opening 279, a non-damping airspring, such as prior art air spring 24 (FIG. 1), may be converted to anair spring that provides damping characteristics such as first exemplaryembodiment air spring 224 of the present invention. In this manner,axle/suspension system 10 does not require a shock absorber to providedamping to the axle/suspension system, thus reducing the weight of theaxle/suspension system. Further, first exemplary embodiment air spring224 of the present invention provides damping characteristics withoutrequiring a custom design and manufacturing process, as an existingdesigned and manufactured piston 242 is utilized, resulting in adesirable decrease in design and manufacturing costs when compared tothe prior art air spring with damping characteristics, such as prior artair spring 124 (FIG. 4). As a result, air spring 224 of the presentinvention converts non-damping air springs, such as prior art air spring24, to an air spring with damping characteristics, in an economicalmanner without an undesirable increase in manufacturing and designcosts, and also avoiding the potential deficiencies of the “take-apart”air spring design.

It should be understood that first exemplary embodiment air spring 224could also be utilized in conjunction with a “take-apart” air springdesign having an open bottom, without changing the overall concept oroperation of the present invention. In such an application, continuousopening 279 is formed through the piston top plate, as the “take-apart”air spring design typically does not include a retaining plate. Disc 270is attached to the open bottom of the piston of the “take-apart” airspring design, and as a result, allows a non-damping “take-apart” airspring design to be converted to a damping “take-apart” air springdesign that includes damping characteristics similar to the “molded-in”air spring design described above.

Turning to FIG. 8, a second exemplary embodiment air spring 324 of thepresent invention, is shown mounted on prior art axle/suspension system10, described in detail above.

Second exemplary embodiment air spring 324 is similar to prior art airspring 24 with respect to its structure, but with some differences thatinclude modification to provide integration of the beam mountingpedestal and damping characteristics by including a disc 370, an opening374 and an opening 375, as will be described below. Second exemplaryembodiment air spring 324 generally includes a bellows 341, a bellowstop plate 343, and a piston 342. Top plate 343 includes a pair offasteners 345, each formed with an opening 346. Fasteners 345 areutilized to mount air spring 324 to an air spring plate (not shown) thatin turn is mounted to main member 12 (FIG. 8). Piston 342 is generallycylindrical-shaped and includes a sidewall 344, a flared portion 347,and a top plate 382.

With additional reference to FIG. 9, a bumper 381 is disposed on a topsurface of a retaining plate 386. Retaining plate 386, bumper 381, andpiston top plate 382 are each formed with aligned openings 360, 362, and364, respectively. A fastener 351 is disposed through piston top plateopening 364, retaining plate opening 360, and bumper opening 362. Awasher (not shown) and a nut (not shown) are threadably disposed onfastener 351 to mount bumper 381 and retaining plate 386 on the topsurface of piston top plate 382. Retaining plate 386 includes a flaredend 380 that is molded into the lower end of bellows 341, which holdsthe bellows in place on piston 342 and forms an airtight seal betweenthe bellows and the piston. Thus, second exemplary embodiment air spring324 is known as a “molded-in” air spring design. It should be understoodthat flared end 380 of retaining plate 386 could also be separate fromthe lower end of the bellows 341, whereby the flared end would captureand hold the lower end of the bellows in place on piston 342 to form anairtight seal between the bellows and the piston, without changing theoverall concept or operation of the present invention. Bellows 341,retaining plate 386, and the bellows top plate (not shown) generallydefine a bellows chamber 398 having an interior volume V₂ at standardride height. Bellows chamber 398 preferably has a volume of from about305 in.³ to about 3000 in.³. More preferably, bellows chamber 398 has avolume of about 485 in.³. Bumper 381 is formed from rubber, plastic orother compliant material and extends generally upwardly from retainingplate 386 mounted on piston top plate 382. Bumper 381 serves as acushion between piston top plate 382 and the underside of the bellowstop plate 343 in order to prevent the plates from damaging one anotherduring operation of the vehicle.

Second exemplary embodiment air spring 324 is formed with an upwardlyextending central hub 352 attached to sidewall 344 in a well-knownmanner. Central hub 352 is formed with an opening 353 that is continuouswith top plate opening 364. A plurality of ribs 372 extend radiallybetween central hub 352 and sidewalls 344 to provide structural supportto second exemplary embodiment air spring 324 of the present invention.

In accordance with one of the primary features of the present invention,generally cup-shaped disc 370 is attached to the bottom of piston 342 ofsecond exemplary embodiment air spring 324 of the present invention.Cup-shaped disc 370 includes a disc base 390 and a vertical sidewall391. Vertical sidewall 391 extends upwardly from disc base 390 tofacilitate a sealing attachment to piston 342, as will be describedbelow.

More specifically, disc base 390 is formed with an opening 376 thataligns with opening 353 of piston central hub 352. Fastener 351 extendsdownwardly through piston hub central opening 353, through disc opening376, and through an opening 319 formed in beam rear end 26. A washer 325and a nut 377 are threadably engaged with the bottom end of fastener 351to sealingly attach cup-shaped disc 370 to first exemplary embodimentair spring 324, and attach the piston of the air spring to the beam.Therefore, cup-shaped disc 370 is attached to beam 18 without the use ofa beam mounting pedestal, such as beam mounting pedestal 130 (FIG. 2),because cup-shaped disc 370 integrates the beam mounting pedestal intoits structure. Once attached, an upper surface 393 of an interiorvertical wall 394 of disc base 390 of cup-shaped disc 370 mates with alower surface 387 of sidewall 344, and a top edge 392 of disc verticalsidewall 391 mates with a lower surface 348 of flared portion 347 ofpiston 342 to provide an airtight sealing engagement with the piston.Additionally, an upper surface 365 of a central portion 373 ofcup-shaped disc 370 mates with a lower surface 354 of central hub 352 toprovide a sealing engagement with piston 342. In this manner, cup-shapeddisc 370, piston top plate 382, and piston sidewall 344 define a pistonchamber 399 having an interior volume V_(I). Piston chamber 399generally is able to withstand the required burst pressure of theaxle/suspension system 10 (FIG. 5) during vehicle operation. Pistonchamber 399 preferably has a volume of from about 105 in.³ to about 550in.³. More preferably, piston chamber 399 has a volume of about 240in.³. It is important to note that cup-shaped disc 370 may be attachedat different locations on piston 342 to vary the volume V₁ based on thespecific application of the heavy-duty vehicle (not shown) to facilitateoptimization of damping characteristics of air spring 324 of the presentinvention. Optionally, the attachment of cup-shaped disc 370 to piston342 may be supplemented by additional attachment means such as welding,soldering, crimping, friction welding, an O-ring, a gasket, adhesive orthe like. Alternatively, the attachment of cup-shaped disc 370 to piston342 may be accomplished via means other than fastener 351, such as othertypes of fasteners, welding, soldering, crimping, friction welding,adhesives and the like, without changing the overall concept oroperation of the present invention. In addition, cup-shaped disc 370 maybe composed of metal, plastic, and/or composite material, or othermaterials known to those skilled in the art, without changing theoverall concept or operation of the present invention.

In accordance with another of the primary features of the presentinvention, opening 374 is formed in retaining plate 386 and alignedopening 375 is formed in top plate 382 of piston 342. More particularly,aligned openings 374,375 are adjacent to bumper 381. Openings 374,375are generally cylindrical-shaped but may include other shapes includingoval, elliptical or other shapes without changing the overall concept oroperation of the present art. Aligned openings 374,375 together form acontinuous opening 379 that allows piston chamber 399 to fluidlycommunicate with bellows chamber 398. Alternatively, openings 374,375may include a spring pin (not shown), or a self-tapping screw with anintegral opening, or other similar conduit that provides communicationof fluid or air between piston chamber 399 and bellows chamber 398during operation of the vehicle. In this manner, damping characteristicsare provided to second exemplary embodiment air spring 324 of thepresent invention. Continuous opening 379 preferably has a crosssectional area of from about 0.009 in.² to about 0.13 in.². Morepreferably, continuous opening 379 has a cross sectional area of about0.06 in.².

It is contemplated that the ratio of the cross-sectional area of opening379 measured in in.² to the volume of piston chamber 399 measured inin.³ to the volume of bellows chamber 398 measured in in.³ is in therange of ratios of from about 1:403:2,346 to about 1:61,111:333,333.This is an inclusive range that could be alternatively expressed as1:403-61,111:2,346-333,333, including any combination of ratios inbetween, and, for example, would necessarily include the followingratios 1:403:333,333 and 1:61,111:2,346.

As shown in FIGS. 8-9, with the attachment of cup-shaped disc 370 topiston 342, and the disc to beam 18, a damping feature is provided tosecond exemplary embodiment air spring 324 of the present invention,which doubles as a mount for the air spring to the beam. Morespecifically, when axle 32 of axle/suspension system 10 experiences ajounce event, such as when the vehicle wheels encounter a curb or araised bump in the road, the axle moves vertically upwardly toward thevehicle chassis. In such a jounce event, bellows chamber 398 iscompressed by axle/suspension system 10 as the wheels of the vehicletravel over the curb or the raised bump in the road. The compression ofair spring bellows chamber 398 causes the internal pressure of thebellows chamber to increase. Therefore, a pressure differential iscreated between bellows chamber 398 and piston chamber 399. Thispressure differential causes air to flow from bellows chamber 398,through continuous opening 379 and into piston chamber 399. The flow ofair between bellows chamber 398 into piston chamber 399 throughcontinuous opening 379 causes damping to occur. As an additional resultof the airflow through continuous opening 379, the pressure differentialbetween bellows chamber 398 and piston chamber 399 is reduced. Aircontinues to flow through continuous opening 379 until the pressures ofpiston chamber 399 and bellows chamber 398 have equalized.

Conversely, when axle 32 of axle/suspension system 10 experiences arebound event, such as when the vehicle wheels encounter a large hole ordepression in the road, the axle moves vertically downwardly away fromthe vehicle chassis. In such a rebound event, bellows chamber 398 isexpanded by axle/suspension system 10 as the wheels of the vehicletravel into the hole or depression in the road. The expansion of airspring bellows chamber 398 causes the internal pressure of the bellowschamber to decrease. As a result, a pressure differential is createdbetween bellows chamber 398 and piston chamber 399. This pressuredifferential causes air to flow from piston chamber 399, throughcontinuous opening 379 and into bellows chamber 398. The flow of airthrough continuous opening 379 causes damping to occur. As an additionalresult of the airflow through continuous opening 379, the pressuredifferential between bellows chamber 398 and piston chamber 399 isreduced. Air will continue to flow through continuous opening 379 untilthe pressures of piston chamber 399 and bellows chamber 398 haveequalized. When little or no suspension movement has occurred over aperiod of several seconds the pressure of bellows chamber 398 and pistonchamber 399 can be considered equal.

As a result of attaching circular disc 370 to piston 342, and providingopening 374 in retaining plate 386 and opening 375 in top plate 382 ofthe piston, collectively, continuous opening 379, a non-damping airspring, such as prior art air spring 24 (FIG. 1), may be converted to anair spring that provides damping characteristics such as secondexemplary embodiment air spring 324 of the present invention. In thismanner, axle/suspension system 10 does not require shock absorber 40(FIG. 1) to provide damping to the axle/suspension system, thus reducingthe weight of the axle/suspension system. Further, second exemplaryembodiment air spring 324 of the present invention provides dampingcharacteristics without requiring a custom design and manufacturingprocess, as an existing designed and manufactured piston 342 isutilized, resulting in a desirable decrease in design and manufacturingcosts when compared to prior art air springs with dampingcharacteristics such as prior art air spring 124 (FIG. 4). Moreover,second exemplary embodiment air spring 324 with cup-shaped disc 370 doesnot require a discrete beam mounting pedestal, thus desirably reducingweight and desirably reducing the amount of time needed to install theair spring of the present invention. As a result, air spring 324 of thepresent invention converts non-damping air springs, such as prior artair spring 24, to an air spring with damping characteristics, in aneconomical manner without an undesirable increase in manufacturing anddesign costs, and also avoiding the potential deficiencies of the“take-apart” air spring design.

It should be understood that second exemplary embodiment air spring 324could also be utilized in conjunction with a “take-apart” air springdesign having an open bottom, without changing the overall concept oroperation of the present invention. In such an application, continuousopening 379 is formed only through the piston top plate, as the“take-apart” air spring design typically does not include a retainingplate. Disc 370 is attached to the open bottom of the piston of the“take-apart” air spring design, and as a result, allows a non-damping“take-apart” air spring design to be converted to a damping “take-apart”air spring design that has damping characteristics similar to the“molded-in” air spring design described above.

Turning to FIG. 10, a third exemplary embodiment air spring 424 of thepresent invention is shown. Third exemplary embodiment 424 is utilizedon prior art axle/suspension system 10, described in detail above. Thirdexemplary embodiment air spring 424 is similar to prior art air spring24 with respect to its structure, but with some differences that includemodification to provide damping characteristics by including a disc 470and a threaded rod 488 formed with an opening 495, as will be describedbelow. Third exemplary embodiment air spring 424 generally includes abellows 441, a bellows top plate 443, and a piston 442. Bellows topplate 443 is formed with a pair of openings 446 through which a pair offasteners 445 are disposed. Fasteners 445 are utilized to mount airspring 424 to an air spring plate (not shown), that in turn is mountedto the main member (not shown) of the axle/suspension system (notshown). Piston 442 is generally cylindrical-shaped and includes asidewall 444, a flared portion 447, and a top plate 482, as will bedescribed below.

A bumper 481 is disposed on a top surface of a retaining plate 486.Retaining plate 486, bumper 481, and piston top plate 482 are eachformed with an aligned opening 460, 462, and 464. Threaded rod 488extends upwardly through piston top plate opening 464, retaining plateopening 460, and bumper opening 462. A washer 483 and a nut 484 aredisposed on threaded rod 488 to mount bumper 481 and retaining plate 486on the top surface of piston top plate 482. Retaining plate 486 includesa flared end 480 that captures and holds the lower end of bellows 441 inplace on piston 442 to form an airtight seal between the bellows and thepiston. Thus, third exemplary embodiment air spring 424 is known as a“molded-in” air spring design. It should be understood that retainingplate 486 could also be integrally molded into the lower end of bellows441, without changing the overall concept or operation of the presentinvention. Bellows 441, retaining plate 486, and bellows top plate 443generally define a bellows chamber 498 having an interior volume V₂ atstandard ride height. Bellows chamber 498 preferably has a volume offrom about 305 in.³ to about 3000 in.³. More preferably, bellows chamber498 has a volume of about 485 in.³. Bumper 481 is formed from rubber,plastic or other compliant material and extends generally upwardly fromretaining plate 486 mounted on piston top plate 482. Bumper 481 servesas a cushion between piston top plate 482 and the underside of bellowstop plate 443 to prevent the plates from damaging one another duringoperation of the vehicle.

Third exemplary embodiment air spring 424 is formed with an upwardlyextending central hub 452 attached to sidewall 444 in a well-knownmanner. Central hub 452 includes an opening 453 that is continuous withtop plate opening 464 and through which threaded rod 488 is disposed, aswill be described below. A plurality of ribs 472 extend radially betweencentral hub 452 and sidewall 444 to provide structural support to thirdexemplary embodiment air spring 424.

With continued reference to FIGS. 10-11, and in accordance with one ofthe primary features of the present invention, generally circular disc470 is attached to the bottom of piston 442 of third exemplaryembodiment air spring 424 of the present invention. More specifically,circular disc 470 includes a base 490 and a vertical sidewall 491 thatextends vertically upwardly from the base. Base 490 is formed with acentral opening 493 that aligns with opening 453 of piston central hub452. Base 490 is also formed with a second opening 496 that is radiallyspaced from first opening 493. It should be understood that secondopening 496 could be formed in base 490 at any accessible locationwithout changing the overall concept or operation of the presentinvention. Threaded rod 488 extends downwardly through piston centralhub opening 453, through disc opening 493, through an opening (notshown) formed in the beam mounting pedestal (not shown), and through anopening formed in the top wall of beam rear end (not shown). A nut (notshown) is threaded onto the bottom end of the threaded rod to sealinglyattach circular disc 470 to third exemplary embodiment air spring 424,and also attaches the piston of the air spring to the beam of theaxle/suspension system (not shown). Once attached, disc verticalsidewall 491 sealingly mates with piston sidewall 444, as will bediscussed below. More particularly, vertical sidewall 491 of circulardisc 470 matingly engages sidewall 444 of piston 442 to provide asealing engagement of the disc to the piston. More specifically, anouter surface 492 of vertical sidewall 491 of circular disc 470 mateswith an inner surface 489 of lower portion 487 of sidewall 444 to forman airtight seal. Optionally, the attachment of circular disc 470 topiston 442 may be supplemented by additional attachment means such aswelding, soldering, crimping, friction welding, an O-ring, a gasket,adhesive or the like. Alternatively, the attachment of circular disc 470to piston 442 may be accomplished via alternative means, such asfasteners, welding, soldering, crimping, friction welding, adhesives andthe like, without changing the overall concept or operation of thepresent invention. Circular disc 470 may be composed of metal, plastic,and/or composite material or other materials known to those skilled inthe art, without changing the overall concept or operation of thepresent invention. As a result of the sealing engagement of circulardisc 470 to the bottom of piston 442, the disc, piston top plate 482,and piston sidewall 444 define a sealed piston chamber 499 having aninterior volume V₁. Piston chamber 499 generally is able to withstandthe required burst pressure of the axle/suspension system (not shown)during vehicle operation. Piston chamber 499 preferably has a volume offrom about 105 in.³ to about 550 in.³. More preferably, piston chamber499 has a volume of about 240 in.³.

In accordance with another of the primary features of the presentinvention, threaded rod 488 is formed with opening 495 that extendsthrough the entire length of the threaded rod. A conduit 494 having acontinuous opening is in fluid communication with the bottom end ofthreaded rod opening 495, and is disposed through and attached, by anysuitable means, to opening 496 formed in circular disc 470. Conduit 494and threaded rod opening 495 provide fluid communication between bellowschamber 498 and piston chamber 499. The opening in conduit 494 andthreaded rod opening 495 each preferably have a cross sectional area offrom about 0.009 in.² to about 0.13 in.². More preferably, the openingin conduit 494 and threaded rod opening 495 each have a cross sectionalarea of about 0.06 in.².

It is contemplated that the ratio of the cross-sectional area of theopening in conduit 494 and threaded rod opening 495 measured in in.²tothe volume of piston chamber 499 measured in in.³ to the volume ofbellows chamber 498 measured in in.³ is in the range of ratios of fromabout 1:403:2,346 to about 1:61,111:333,333. This is an inclusive rangethat could be alternatively expressed as 1:403-61,111:2,346-333,333,including any combination of ratios in between, and, for example, wouldnecessarily include the following ratios 1:403:333,333 and1:61,111:2,346.

More specifically, when the axle (not shown) of the axle/suspensionsystem (not shown) experiences a jounce event, such as when the vehiclewheels encounter a curb or a raised bump in the road, the axle movesvertically upwardly toward the vehicle chassis. In such a jounce event,bellows chamber 498 is compressed by the axle/suspension system (notshown) as the wheels of the vehicle travel over the curb or the raisedbump in the road. The compression of air spring bellows chamber 498causes the internal pressure of the bellows chamber to increase.Therefore, a pressure differential is created between bellows chamber498 and piston chamber 499. This pressure differential causes air toflow from bellows chamber 498, through threaded rod opening 495, throughconduit 494 and into piston chamber 499. The flow of air between bellowschamber 498 into piston chamber 499 through threaded rod opening 495 andconduit 494 causes damping to occur. As an additional result of the airflow through threaded rod opening 495 and conduit 494, the pressuredifferential between bellows chamber 498 and piston chamber 499 isreduced. Air continues to flow through threaded rod opening 495 andconduit 494 until the pressure of piston chamber 499 and bellows chamber498 have equalized. Conversely, when the axle (not shown) of theaxle/suspension system (not shown) experiences a rebound event, such aswhen the vehicle wheels encounter a large hole or depression in theroad, the axle moves vertically downwardly away from the vehiclechassis. In such a rebound event, bellows chamber 498 is expanded by theaxle/suspension system (not shown) as the wheels of the vehicle travelinto the hole or depression in the road. The expansion of air springbellows chamber 498 causes the internal pressure of the bellows chamberto decrease. As a result, a pressure differential is created betweenbellows chamber 498 and piston chamber 499. This pressure differentialcauses air to flow from piston chamber 499, through conduit 494, throughthreaded rod opening 495, and into bellows chamber 498. The flow of airthrough conduit 494 and threaded rod opening 495 causes damping tooccur. As an additional result of the air flow through conduit 494 andthreaded rod opening 495, the pressure differential between bellowschamber 498 and piston chamber 499 is reduced. Air will continue to flowthrough conduit 494 and threaded rod opening 495 until the pressure ofpiston chamber 499 and bellows chamber 498 have equalized. When littleor no suspension movement has occurred over a period of several seconds,the pressure of bellows chamber 498 and piston chamber 499 can beconsidered equal.

As a result of attaching circular disc 470 with openings 496 to piston442 and providing threaded rod opening 495 and conduit 494, anon-damping air spring such as prior art air spring 24, may be convertedto an air spring that includes damping characteristics such as thirdexemplary embodiment air spring 424 of the present invention. In thismanner, the axle/suspension system (not shown) does not require a shockabsorber to provide damping to the axle/suspension system, thus reducingthe weight of the axle/suspension system. Third exemplary embodiment airspring 424 of the present invention provides damping characteristicswithout requiring a custom design and manufacturing process, as anexisting designed and manufactured piston 442 is utilized, resulting ina desirable decrease in design and manufacturing costs when compared toa prior art air spring with damping characteristics, such as prior artair spring 124 (FIG. 4). As a result, air spring 424 of the presentinvention converts non-damping air springs, such as prior art air spring24 (FIG. 1), to an air spring with damping characteristics in aneconomical manner, without an undesirable increase in manufacturing anddesign costs, and also avoiding the potential deficiencies of the“take-apart” air spring design.

It should be understood that third exemplary embodiment air spring 424could also be utilized in conjunction with a “take-apart” air springdesign having an open bottom, without changing the overall concept oroperation of the present invention. In such an application, disc 470including threaded rod 488 and conduit 494 is attached to the openbottom of the piston of the “take-apart” air spring design, and as aresult, allows a non-damping “take-apart” air spring design to beconverted to a damping “take-apart” air spring design that has dampingcharacteristics similar to the “molded-in” air spring design describedabove.

Referring now to FIGS. 12 and 13, discs 570 and 670 are alternativeconfigurations of discs that can be attached or mated to the bottom of apiston, utilizing all types of attachments including friction welding,soldering, coating, crimping, welding, snapping, screwing, O-ring,sonic, glue, press, melting, expandable sealant, press-fit, bolt, latch,spring, adhesive bond, laminate, tape, tack, adhesive, shrink fit, andthe like, and/or any combination listed, without changing the overallconcept or operation of the present invention. It is even contemplatedthat discs 570 and 670 may be composed of materials known by those inthe art other than metal, plastic, and/or composite material withoutchanging the overall concept or operation of the present invention.

The air spring for heavy-duty vehicles with damping characteristics ofthe present invention overcomes the problems associated with prior artair springs by eliminating the use of shock absorbers while converting anon-damping air spring with a “molded-in” end closure into an air springthat provides damping characteristics. It also allows for the use ofdifferent piston/pedestal combinations to be used in the air spring sothat the volume of the piston can be varied along with the opening sizebetween the piston chamber and the bellows chamber to optimize thedamping characteristics of the air spring. Additionally, the air springfor heavy-duty vehicles with damping characteristics of the presentinvention provides an air spring with damping characteristics that maybe optimized for different uses without requiring custom designed andmanufactured air springs for a specific application as required by priorart air springs with damping characteristics.

The present invention also includes a method of converting a non-dampingair spring to an air spring with damping characteristics. The methodincludes steps in accordance with the description and structure that ispresented above and shown in FIGS. 5-13.

It is contemplated that exemplary embodiment air springs 224,324,424 ofthe present invention could be utilized on tractor-trailers orheavy-duty vehicles, such as buses, trucks, trailers and the like,having one or more than one axle without changing the overall concept oroperation of the present invention. It is further contemplated thatexemplary embodiment air springs 224,324,424 could be utilized onvehicles having frames or subframes which are moveable or non-movablewithout changing the overall concept or operation of the presentinvention. It is yet even further contemplated that exemplary embodimentair springs 224,324,424 could be utilized on all types of air-rideleading and/or trailing arm beam-type axle/suspension system designsknown to those skilled in the art without changing the overall conceptor operation of the present invention. It is also contemplated thatexemplary embodiment air springs 224,324,424 could be utilized onaxle/suspension systems having an overslung/top-mount configuration oran underslung/bottom-mount configuration, without changing the overallconcept or operation of the present invention. It is also contemplatedthat exemplary embodiment air springs 224,324,424 could be utilized inconjunction with other types of air-ride rigid beam-type axle/suspensionsystems such as those using U-bolts, U-bolt brackets/axle seats and thelike, without changing the overall concept or operation of the presentinvention. It is further contemplated that exemplary embodiment airsprings 224,324,424 could be formed from various materials, includingcomposites, metal and the like, without changing the overall concept oroperation of the present invention. It is even contemplated thatexemplary embodiment air springs 224,324,424 could be utilized incombination with prior art shock absorbers and other similar devices andthe like, without changing the overall concept or operation of thepresent invention.

It is contemplated that discs 270,370,470,570,670 may be attached topistons 242,342,442, respectively, utilizing other attachments such asfriction welding, vibration, soldering, coating, crimping, welding,snapping, screwing, O-ring, sonic, glue, press, melting, expandablesealant, press-fit, bolt, latch, spring, adhesive bond, laminate, tape,tack, adhesive, shrink fit, and/or any combination listed withoutchanging the overall concept or operation of the present invention. Itis even contemplated that discs 270,370,470,570,670 may be composed ofmaterials known by those in the art other than metal, plastic, and/orcomposite material without changing the overall concept or operation ofthe present invention.

It is contemplated that openings 274,275,374,375 of first and secondexemplary embodiments 224,324 could be formed in a different locationwithin retaining plates 286,386 and top plates 282,382 of pistons242,342, respectively, without changing the overall concept or operationof the present invention. It is further contemplated that any number ofopenings 274,275,374,375 may be formed in retaining plates 286,386 andtop plates 282,382 of pistons 242,342, respectively, such as multiplesmall openings without changing the overall concept or operation of thepresent invention.

It is contemplated that discs 270,370,470,570,670 may extend verticallyfurther up vertical sidewalls 391,491 without changing the overallconcept or operation of the present invention. It is also contemplatedthat discs 270,370,470570,670 could have variable thicknesses beingeither uniform or non-uniform, without changing the overall concept oroperation of the present invention. It is even contemplated that lip 278may extend vertically higher without changing the overall concept oroperation of the present invention. It is further contemplated thatdiscs 270,470,570,670 may include structure to directly attach to eachrespective beam 18 similar to the structure of disc 370 without changingthe overall concept or operation of the present invention. It is evenfurther contemplated that discs 270,370,470,570,670 could include agroove to facilitate a sealing attachment to pistons 242,342,442,respectively, without changing the overall concept or operation of thepresent invention.

It is contemplated that disc 470 may include any number of openings 496and/or the openings located in a different location within therespective disc without changing the overall concept or operation of thepresent invention.

It is contemplated that conduit 494 may be composed of flexiblematerials such as rubber, plastic or other materials known to thoseskilled in the art without changing the overall concept or operation ofthe present invention. It is further contemplated that threaded rod 488may include a conduit or other means disposed in opening 495 tofacilitate fluid communication, without changing the overall concept oroperation of the present invention

The present invention has been described with reference to specificembodiments. It is to be understood that this illustration is by way ofexample and not by way of limitation. Potential modifications andalterations will occur to others upon a reading and understanding ofthis disclosure, and it is understood that the invention includes allsuch modifications and alterations and equivalents thereof.

Accordingly, the air spring with damping characteristics for heavy-dutyvehicles is simplified, provides an effective, safe, inexpensive andefficient structure and method which achieves all the enumeratedobjectives, provides for eliminating difficulties encountered with priorart air springs for heavy-duty vehicles, and solves problems and obtainsnew results in the art.

In the foregoing description, certain terms have been used for brevity,clearness and understanding; but no unnecessary limitations are to beimplied therefrom beyond the requirements of the prior art, because suchterms are used for descriptive purposes and are intended to be broadlyconstrued.

Moreover, the description and illustration of the invention is by way ofexample, and the scope of the invention is not limited to the exactdetails shown or described.

Having now described the features, discoveries and principles of theinvention, the manner in which the air spring with dampingcharacteristics for heavy-duty vehicles is used and installed, thecharacteristics of the construction, arrangement and method steps, andthe advantageous, new and useful results obtained; the new and usefulstructures, devices, elements, arrangements, process, parts andcombinations are set forth in the appended claims.

What is claimed is:
 1. An air spring with damping characteristics for asuspension assembly of a heavy-duty vehicle comprising: a bellows and apiston, said bellows including a bellows chamber, the bellows attachedto a main member of said heavy-duty vehicle, and attached to saidpiston, the piston having an open bottom, said open bottom of saidpiston being sealingly closed by a disc attached to the open bottom,whereby the piston and said disc define a piston chamber, said pistonmounted on said suspension assembly of said heavy-duty vehicle, saidbellows chamber and said piston chamber being in fluid communicationwith each other via at least one opening, wherein airflow between thebellows chamber and the piston chamber provides damping to thesuspension assembly of said heavy-duty vehicle.
 2. The air spring withdamping characteristics for a suspension assembly of a heavy-dutyvehicle of claim 1, said piston further comprising a flared portion anda piston sidewall, said disc being generally circular-shaped, furthercomprising a continuous raised lip, wherein said continuous raised lipis formed on a disc top surface along a periphery of said disc, withsaid continuous raised lip disposed generally between said flaredportion and said piston sidewall for reinforcing said attachment of saiddisc to said piston.
 3. The air spring with damping characteristics fora suspension assembly of a heavy-duty vehicle of claim 1, said discfurther comprising a groove formed in a top surface of said discdisposed circumferentially around said disc, and configured to mate witha lower surface of said piston for reinforcing said attachment of saiddisc to said piston.
 4. The air spring with damping characteristics fora suspension assembly of a heavy-duty vehicle of claim 3, an O-ringbeing disposed in said groove for reinforcing said attachment of saiddisc to said piston.
 5. The air spring with damping characteristics fora suspension assembly of a heavy-duty vehicle of claim 1, said pistonfurther comprising a piston sidewall and a central hub, said disc beinggenerally cup-shaped, further comprising a base, a vertical sidewall,and a central portion, wherein said base mates with a lower surface ofsaid piston sidewall, said vertical sidewall mates with said piston, andsaid central portion mates with said central hub for reinforcing saidattachment of said disc to said piston.
 6. The air spring with dampingcharacteristics for a suspension assembly of a heavy-duty vehicle ofclaim 1, said bellows chamber including a volume of from about 305 in.³to about 3000 in.³.
 7. The air spring with damping characteristics for asuspension assembly of a heavy-duty vehicle of claim 1, said pistonchamber including a volume of from about 105 in.³ to about 550 in.³. 8.The air spring for a heavy-duty vehicle of claim 1, said at least oneopening including a cross sectional area of from about 0.009 in.² toabout 0.13 in.².
 9. The air spring for a heavy-duty vehicle of claim 1,wherein a ratio of a cross sectional area of said at least one openingmeasured in in.² to a volume of said piston chamber measured in in.³ toa volume of said bellows chamber measured in in.³ is in a range ofratios of from about 1:403:2,346 to about 1:61,111:333,333.
 10. The airspring with damping characteristics for a suspension assembly of aheavy-duty vehicle of claim 1, said at least one opening comprising: athreaded rod, said threaded rod formed with an opening through a lengthof the threaded rod, said threaded rod disposed between and in fluidcommunication with said bellows chamber and said piston chamber.
 11. Theair spring with damping characteristics for a suspension assembly of aheavy-duty vehicle of claim 10, said air spring further comprising aconduit, said conduit providing fluid communication between saidthreaded rod opening and said piston chamber.
 12. The air spring withdamping characteristics for a suspension assembly of a heavy-dutyvehicle of claim 1, said attachment of said disc to said open bottom ofsaid piston comprises and adhesive bond or a friction weld.
 13. A methodfor converting a non-damping air spring into an air spring with dampingcharacteristics for a suspension assembly of a heavy-duty vehicle,comprising the following steps: a) providing a bellows and a piston,said bellows including a bellows chamber, said bellows chamber attachedto a main member of said heavy-duty vehicle, and attached to saidpiston, the piston having an open bottom, b) sealingly closing said openbottom of said piston by attaching a disc to the open bottom, wherebythe piston and said disc define a piston chamber, said piston mounted onsaid suspension assembly of the heavy-duty vehicle, said bellows chamberand said piston chamber being in fluid communication with each other viaat least one opening, wherein airflow between the bellows chamber andthe piston chamber provides damping to the suspension assembly of saidheavy-duty vehicle.
 14. The method for converting a non-damping airspring into an air spring with damping characteristics for a suspensionassembly of a heavy-duty vehicle of claim 13, said piston furthercomprising a flared portion and a piston sidewall, said disc beinggenerally circular-shaped, further comprising a continuous raised lip,wherein said continuous raised lip is formed on a disc top surface alonga periphery of said disc, with said continuous raised lip disposedgenerally between said flared portion and said piston sidewall forreinforcing said attachment of said disc to said piston.
 15. The methodfor converting a non-damping air spring into an air spring with dampingcharacteristics for a suspension assembly of a heavy-duty vehicle ofclaim 13, said disc further comprising a groove formed in a top surfaceof said disc disposed circumferentially around said disc, and configuredto mate with a lower surface of said piston for reinforcing saidattachment of said disc to said piston.
 16. The method for converting anon-damping air spring into an air spring with damping characteristicsfor a suspension assembly of a heavy-duty vehicle of claim 15, an O-ringbeing disposed in said groove for reinforcing said attachment of saiddisc to said piston.
 17. The method for converting a non-damping airspring into an air spring with damping characteristics for a suspensionassembly of a heavy-duty vehicle of claim 13, said piston furthercomprising a piston sidewall, and a central hub, said disc beinggenerally cup-shaped, further comprising a base, a vertical sidewall,and a central portion, wherein said base mates with a lower surface ofsaid piston sidewall, said vertical sidewall mates with said piston, andsaid central portion mates with said central hub for reinforcing saidattachment of said disc to said piston.
 18. The method for converting anon-damping air spring into an air spring with damping characteristicsfor a suspension assembly of a heavy-duty vehicle of claim 13, saidbellows chamber including a volume of from about 305 in.³ to about 3000in.³.
 19. The method for converting a non-damping air spring into an airspring with damping characteristics for a suspension assembly of aheavy-duty vehicle of claim 13, The air spring with dampingcharacteristics for a suspension assembly of a heavy-duty vehicle ofclaim 1, said piston chamber including a volume of from about 105 in.³to about 550 in.³.
 20. The method for converting a non-damping airspring into an air spring with damping characteristics for a suspensionassembly of a heavy-duty vehicle of claim 13, said at least one openingincluding a cross sectional area of from about 0.009 in.² to about 0.13in.².
 21. The method for converting a non-damping air spring into an airspring with damping characteristics for a suspension assembly of aheavy-duty vehicle of claim 13, wherein a ratio of a cross sectionalarea of said at least one opening measured in in.² to a volume of saidpiston chamber measured in in.³ to a volume of said bellows chambermeasured in in.³ is in a range of ratios of from about 1:403:2346 toabout 1:61,111:333,333.
 22. The method for converting a non-damping airspring into an air spring with damping characteristics for a suspensionassembly of a heavy-duty vehicle of claim 13, said at least one openingcomprising: a threaded rod, said threaded rod formed with an openingthrough a length of the threaded rod, said threaded rod disposed betweenand in fluid communication with said bellows chamber and said pistonchamber.
 23. The method for converting a non-damping air spring into anair spring with damping characteristics for a suspension assembly of aheavy-duty vehicle of claim 22, said air spring further comprising aconduit attached to and in fluid communication with said threaded rodopening , said conduit providing fluid communication between saidthreaded rod opening and said piston chamber.
 24. The method forconverting a non-damping air spring into an air spring with dampingcharacteristics for a suspension assembly of a heavy-duty vehicle ofclaim 13, said attachment of said disc to said open bottom of saidpiston comprises an adhesive bond or a friction weld.